It's down in the System Requirements. there are some Steamworks games Amazon sells that don't use Steam (I'm not sure how that works), one of them in L.A. Noire, but it won't have Steam listed down in the system Requirements if thats the case.

I've never been so successful resisting myself from buying games. Partially because i already have 3/4 of them but partially because they were still too expensive or just not interesting enough. So far i've only bought 2 skins for Killing Floor, F3AR and Shoot Many Robots. In the past i'd spend around 100 EUR by now...